The present invention relates generally to electrical simulators of nuclear fuel assemblies, and more particularly to a heater element design for electrically-powered heater assemblies having concentric fuel tubes.
The heating produced in nuclear fuel assemblies can be simulated in theory by electrically powered assemblies which are designed to represent all or part of an actual fuel assembly. Current machining technology has been successfully applied in the construction of cylindrical rod heater elements for simulation of nuclear fuel rods. However, for other nuclear fuel assembly geometries, such as the concentric cylindrical fuel tubes in the Savannah River Laboratory (SRL) production reactors, current machining technology cannot be used to build electrically powered cylindrical heater tube elements. A major reason is the small thicknesses of the components in a cylindrical heater tube which do not have the material structural strength to withstand machining. Additionally, the design of cylindrical heater elements using only MONEL (Trademark of a nickel-copper alloy and a nontypical nuclear material) and based on current machining technology requires power leads to enter and exit from both ends of the cylindrical heater element. Such designs also contain mechanical components associated with the power leads that perturb the coolant flow at the entrance and exit of the electrically powered simulators.
The need for electrical powered simulators of the production reactor fuel assemblies originates from studies on the safety aspects of these reactors. In accident conditions, such as the loss-of-coolant accident from a failure (break) in a primary reactor coolant system component, the loss of coolant that removes the nuclear generated heat from the core causes the fuel assemblies to go into a sustained heatup. If coolant is not restored the core heatup will result in fuel melting temperatures being reached which is the initial phase of what is termed a "servere reactor accident" in which fuel damage and release of radioactivity occurs. In order to prevent such severe accidents from occurring, or as a minimum reducing the probability of such an accident to a low value (1 in 10.sup.6), accident recovery systems and operator procedures must be developed that would contain or limit the fuel temperatures in accident conditions to the non-damage region. The successful development of systems and procedures depends in part on experimental data obtained from experiments simulating the accident conditions. Understanding the physics involved provides the means to design the methods to limit the fuel temperatures to non-damage values. Thus, the need for accurate simulation of the fuel assemblies with electrically powered simulators becomes apparent. Without very good experimental data the analysis of such accident conditions in the reactors in the reactors is entirely theoretical. Theoretical analyses alone are not sufficient to obtain licensing to operate nuclear plants.
Accordingly, it is an object of the present invention to provide a nuclear fuel assembly electrical simulator having a full scale cross-section with power leads connected only at the top of the simulator.
A further object of the present invention is to provide a simulated nuclear reactor heater assembly which provides prototypical fuel assembly entrance and exit geometry.
Yet another object of the present invention is to provide a simulated nuclear reactor heater assembly with preservation of fuel assembly surface materials that transfer heat to the coolant.